Reliability-based and deterministic design optimization of a FSAE brake pedal: a risk allocation analysis
STRUCTURAL AND MULTIDISCIPLINARY OPTIMIZATION
Authors: Romero, Jose; Queipo, Nestor
Abstract
While probabilistic designs can translate into significant weight savings through better risk allocation, deterministic design optimization remains widely used in industry. To promote the use of probabilistic designs among engineering students and practitioners, this work solves reliability based design optimization (RBDO) and deterministic design optimization (DDO) models of a FSAE brake pedal with multiple failure modes (stress and buckling) with their relative performance evaluated through a risk allocation analysis. The problems of interest were systematically solved through the following steps: i) topology optimization to specify the brake-pedal shape, ii) numerical 3D brake-pedal modeling under uncertainty for stress and buckling analysis, iii) mass (M), maximum von Mises stress (S-max) and buckling load factor (f(buck)) surrogate modeling, iv) global sensitivity analysis and surrogate model selection, and v) surrogate-based RBDO and DDO with risk allocation analysis. Results show that when compared to DDO with alternative safety factors, for the same probability of system failure, the RBDO brake pedal designs were significantly lighter and more robust (less mass variability).
Experimental Demonstration of Real-Time High-Level QAM-Encoded Direct-Detection Optical OFDM Systems
JOURNAL OF LIGHTWAVE TECHNOLOGY
Authors: Chen, Ming; He, Jing; Fan, Qirui; Dong, Ze; Chen, Lin
Abstract
In this paper, high-level quadrature amplitude modulation (QAM)-encoded real-time orthogonal frequency division multiplexing (OFDM) transceivers are implemented with two field programmable gate arrays and high-resolution digital-to-analog converter (DAC) and analog-to-digital converter (ADC). Some key digital signal processing (DSP) algorithms for real-time direct-detection optical OFDM (DDO-OFDM) system are presented and described in detail. To improve the effective number of bits of ADC and reduce quantization noise, the DAC operates at 5 GS/s with an oversampling factor of 2. Meanwhile, the optimal digital clipping ratio at the transmitter is also investigated by numerical simulation to optimize the performance of the real-time transmitter. The results show that the real-time measured BERs after 10-km SSMF are below the hard-decision forward error correction threshold of 3.8 x 10(-3). For comparison, the off-line BER performance is also analyzed using off-line DSP approaches. It shows that there is a negligible power penalty between the offline and real-time processing results. To the best of our knowledge, we have achieved the highest modulation format (1024-QAM) for real-time optical OFDM systems.